1. Field of the Invention
The present invention relates to a deflection angle measuring device, an optical signal switching system, an information recording and replaying system, deflection angle measuring method, and optical signal switching method.
The present application is based on patent application No. 2002-79150 filed in Japan, the content of which is incorporated herein by reference.
2. Description of Related Art
In recent years, technology for optical information communication and optical information recording has been developed tremendously; thus, information transmitting density and information recording density have increased greatly. In this technology area, it is necessary that a technique for measuring and controlling an inclination of an light deflecting mirror accurately so as to be used in for an optical signal switch for optically switching optical fiber networks and relay stations and a tracking-control for an optical pickup in an optical information recording and replaying system improves.
For such a purpose, various sensors for measuring the deflection angle have been proposed conventionally.
Such a conventional technology is disclosed in prior art documents such as Japanese Unexamined Patent Application, Second Publication No. Hei7-66554, Japanese Unexamined Patent Application, First Publication, No. Hei8-227552, Japanese Unexamined Patent Application, First Publication, No. 11-144273, and Japanese Unexamined Patent Application, First Publication, No. 11-144274.
In Japanese Unexamined Patent Application, Second Publication No. Hei7-66554, a device for measuring a relative angle between a light path of a beam which is emitted from an optical pickup to a recording medium and a recording surface on the recording medium. Such a device is provided with an illuminating element for emitting a light to a recording surface and two light receiving element which are disposed on both sides of the illuminating element for detecting a light which is reflected from the recording surface. In this technique, a difference between the amount of the reflected lights which are detected by two light receiving elements are measured so as to measure an amount of inclination of the recording medium.
In Japanese Unexamined Patent Application, First Publication, No. Hei 8-227552, a device for measuring a relative angle between a light path of a beam which is emitted from an optical pickup to a recording surface and a recording surface on the recording medium is also disclosed. This device receives a light which is reflected at the recording medium at a light-receiving surface which is divided in four regions so as to measure an amount of inclination in two directions according to the amount of received light.
Also, in Japanese Unexamined Patent Application, First Publication, No. 11-144273, and Japanese Unexamined Patent Application, First Publication, No. 11-144274, it is disclosed that an angle-measuring light flux is emitted to a galvano-meter mirror which is used for a fine-movement tracking of an optical pickup, and an amount of the light which is reflected there is measured by a light measuring device through a beam splitter of which reflection ratio changes according to an incident angle; thus, an inclination angle is measured.
Also, in particular, a conventional optical signal switching system such as an optical MEMS (Micro Electro Mechanical Systems) switches the angle of a light deflecting mirror at a predetermined deflection angle according to a predetermined signal.